In the RV4 they are either installed on the torque tube between the sticks (same as the RV8) or out in the wing...The preferred location for the RV6 is under the seat pans (per TruTrak - it's the way most -6's are done as far as TruTrak installs go, although there have been the ocassional few in the wingtip with a long pushrod) and in the wing for the 7 & 9 near the bellcrank.
There are a lot of RV4's flying with Trutraks, Navaids and also Trios in them...you shouldn't have a problem.
Cheers,
Stein.